I think the last ditch rifles had fixed rear sights instead of adjustable.
OP, you mention making it a "show piece".
Please realize if you refinish the stock, reblue the metal, etc you ruin the value of the rifle. Maybe a light coat of oil on the metal parts but wouldn't do anything more than that.
Of course, it is yours and do with it what you like. Just understand you ruin the historical value when refinishing.
Thanks for posting! Love these old rifles. Real pieces of history (if that gun could only talk...). Of course I don't understand Japanese so...
That is why I think this rifle was put in a last ditch stock and did not come in it.
I sent him a PM and will meet with him to examine the rifle and let him know exactly what he has.
Also notice in one of his pictures it has the sights that used to have the airplane sights too. or so it seems.